Vehicles include an engine that drives at least one wheel through a transmission. The transmission selectively shifts gear ratios to adjust the speed and torque output to the wheel based on throttle input, vehicle load and other factors. A transmission up-shift enables the engine to drive the wheel at a higher speed with lower torque. A downshift enables the engine to drive the wheel at a lower speed with higher torque.
During driving, tires associated with the driven wheels frictionally engage a road surface. The adhesion or traction of the tires on the road surface is proportional to the vertical load on the wheel, a coefficient of friction between the wheel and the surface. The traction of the tires on the road surface impacts vehicle control. For example, traction on ice is significantly lower than dry pavement.
Transmission shifts may induce torque disturbances in the drivetrain, which may adversely impact wheel traction. The traction loss may be more pronounced during acceleration or turning of the vehicle.